ascending pathways - spinocerebellar tracrs Flashcards
NON-CONSCIOUS PROPRIOCEPTION
Information from skin, muscles & joints to the cerebellum
for coordination of movement
1. Posterior spinocerebellar tract (trunk & LL)
2. Cuneocerebellar tract (trunk & UL equivalent)
3. Anterior spinocerebellar tract (trunk & LL)
4. Rostral spinocerebellar tract (UL equivalent)
Posterior spinocerebellar tract (fibres enter C8 & below)
Collaterals of dorsal column afferent fibres
Synapse with the 2nd order neuron in Clarke’s nucleus C8-L2 (Fibres entering below L2 ascend in fasciculus gracilis until L2)
happens all on same side eg. L leg > Lft spinal cord
clarke’s nucleus
integrates afferent information from proprioceptors and skin receptors
- summarise and sends to cerebellum
- Cuneocerebellar tract (fibres C7 & above)
= UL equivalent of posterior spinocerebellar
There is no Clarke’s nucleus - 1st order neurons ascend in fasciculus cuneatus
- synapse in accessory (lateral) cuneate nucleus in medulla
- Anterior spinocerebellar tract (LL) contralateral
2nd order neuron cell bodies are on the lateral surface of the ventral horn!!
• Spinal border cells in lumbar segments
• Afferents = muscles, skin, interneurons & descending tracts (feedback on intended movement)
• Decussate then ascend as anterior spinocerebellar tract
• Superior cerebellar peduncle to cerebellum
• Decussate again back to original side
- Rostral spinocerebellar tract
• UL equivalent of anterior spinocerebellar
3 main ascending somatosensory pathways from the BODY:
Reach consciousness and 3 neurons 1. Anterolateral (spinothalamic) 2. Dorsal column – medial lemniscus pathway Subconsicous lvl and 2 neurons: 3. Spinocerebellar pathways
3 ascending somatosensory pathways from the HEAD:
- Spinal trigeminothalamic pathway (3)
- Chief sensory trigeminothalamic pathway (3)
- Mesencephalic trigeminothalamic pathway (2)
Trigeminal nuclei:
Trigeminal nuclei: 3 sensory + 1 motor
3 trigeminothalamic pathways:
Mesencephalic = subconscious proprioception (midbrain) Chief sensory = discriminative touch, pressure, conscious proprioception (@ [pons lvl, lateral 2 motor) Spinal = nociception & temperature (midpons > C3)
SPINAL TRIGEMINOTHALAMIC - (3 neurons)
nociception & temperature
• Free nerve endings
• A delta & C fibres
• 1st order neuron cell body in trigeminal ganglion
• 1st order neuron enters pons & descends* to spinal
nucleus
• 2nd order neuron cell body in spinal nucleus (pons,
medulla, Cervical spine – extends to C3)
• Blends with substantia gelatinosa & dorsolateral tract
• 2nd order neurons decussate & join anterolateral tract
• Synapses in VPM thalamus + collaterals to brainstem
• 3rd order neuron ascends via posterior limb internal
capsule
• Post central gyrus, parietal lobe
CHIEF SENSORY TRIGEMINOTHALAMIC - (3 neurons)
Discriminative touch & conscious proprioception
• Skin, proprioceptors & mechanoreceptors from muscles of mastication, facial & extraocular; TMJ; periodontal ligaments
• 1st order neuron cell body in trigeminal ganglion
• 2nd order neuron cell body in chief sensory nucleus
(pons)
• Most 2nd order neurons decussate & join medial
lemniscus
• Synapse in VPM thalamus
• 3rd order neuron ascends via posterior limb
internal capsule
• Post central gyrus, parietal lobe
MESENCEPHALIC TRIGEMINOTHALAMIC
(2 neurons) non-conscious proprioception
proprioceptors, mechanoreceptors from muscles of mastication, gums, teeth hard palate
• 1st order neuron cell body in mesencephalic nucleus (midbrain)!!
• Sends processes to:
• ipsilateral cerebellum via superior cerebellar peduncle
• Trigeminal motor nucleus (reflexes)
• Brainstem reticular formation